In the hearing instrument and mobile communication system industry, one of the primary goals is to make components of small sizes while still maintaining good electroacoustic performance and operability giving good user friendliness and satisfaction. Technical performance data include sensitivity, noise, stability, compactness, robustness and insensitivity to electromagnetic interference (EMI) and other external and environmental conditions. In the past, several attempts have been made to make microphone systems smaller while maintaining or improving their technical performance data.
Another issue within these component industries concerns the ease of integration into the complete system.
EP 561 566 discloses a solid state condenser microphone having a field effect transistor (FET) circuitry and a cavity or sound inlet on the same chip. The techniques and processes for manufacturing a FET circuitry are quite different from the techniques and processes used in manufacturing transducer elements. Consequently, the transducer element and FET system disclosed in EP 561 566 requires two (or possibly more) separate stages of production which by nature makes the manufacturing more complicated and thereby also more costly.
The article “The first silicon-based micro-microphone” published in the Danish journal Elektronik og Data, No. 3, p. 4–8, 1998 discloses how silicon-based microphone systems can be designed and manufactured. The article discloses a three-layer microphone system where a transducer element is flip-chip mounted on an intermediate layer connecting the transducer element to an electronic device, such as an ASIC. The transducer element comprises a movable diaphragm and a substantially stiff back plate. On the opposite side of the transducer element a silicon-based structure forming a back chamber is mounted. It is worth noting that in order for the microphone system to be electrically connected to the surroundings wire bonding or direct soldering is required. The development of combined microelectromechanical systems (MEMS) has progressed significantly over the last years. This has primarily to do with the development of appropriate techniques for manufacturing such systems. One of the advantages of such combined systems relates to the size with which relative complicated systems involving mechanical micro-transducers and specially designed electronics may be manufactured.
It is an object of the present invention to provide a sensor system where the different elements forming the sensor system are flip-chip mounted, applying standard batch-oriented techniques.
It is a further object of the present invention to provide a sensor system suitable for mounting on e.g. PCB's using flip-chip or surface mount technologies and thereby avoid wire bonding or complicated single-chip handling.
It is a still further object of the present invention to provide a sensor system where the distance between the transducer element and the electronics is reduced so as to reduce parasitics and space consumption.